Rack for castors on a chair seat



FIG. 1 is a front elevational view of a rack for castors on a chair seat showing my new design;

FIG. 2 is a rear view of the design;

FIG. 3 is a left side view of the design;

FIG. 4 is a right side view of the design;

FIG. 5 is a top view of the design;

FIG. 6 is a bottom view of the design; and,

FIG. 7 is a perspective view thereof. 

The ornamental design for a rack for castors on a chair seat, as shown. 